IABP is a method for treatment when the heart functions decline due to cardiac insufficiency etc. and is designed to assist heart functions by the insertion of a balloon catheter in the aorta and expanding and contracting the balloon portion along with the beating of the heart.
IABP is a method for treatment when the heart functions decline due to cardiac insufficiency etc. and is designed to assist heart functions by the insertion of a balloon catheter in the aorta and expanding and contracting the balloon portion along with the beating of the heat.
Various balloon catheters used for such IABP have been proposed (Japanese Unexamined Patent Publication (Kokai) No. 63-206255, Japanese Unexamined Patent Publication (Kokai) No. 62-11456, etc.)
In such balloon catheters, there is known a so-called double lumen type balloon catheter in which the balloon catheter is inserted into a blood vessel along a guidewire so as to enable the balloon portion to be guided to a predetermined position close to the heart in the arterial blood vessel. This balloon catheter has an inner tube arranged inside an outer tube forming the catheter tube. The lumen of the inside of the outer tube serves as a flow channel for a shuttle gas for causing the balloon portion to expand or contract, while the lumen of the inner tube serves as a through hole for the guidewire for guiding the balloon portion to the predetermined position near the heart in the artery.
In such a balloon catheter having an inner tube, however, there is the following problem. That is, the outer tube forming the catheter tube is supposed to be inserted inside the artery of the patient, so considering the discomfort to the patient, in particular the circulation of the blood from the point of insertion to the tissue at the terminal side, preferably should be as small in outer diameter as possible.
If the outer diameter of the outer tube is small, however, the cross-section of the flow channel of the lumen formed inside it becomes small. The inside of the outer tube also has the inner tube disposed in it so the actual cross-sectional area of the flow channel for the circulation of the gas is reduced even more. To enlarge the actual cross-sectional area of the flow channel in the lumen of the outer tube, it is preferable that the outer diameter of the inner tube also be small. The lumen of the inner tube, however, has the guidewire inserted through it, so there is a limit to how small the outer diameter of the inner tube can be made.
The lumen of the outer tube other than the cross-section of the inner tube is passed through by the gas for causing the expansion and contraction of the balloon portion. If the outer diameter of the outer tube is made small, the cross-sectional area of the flow channel of the lumen becomes increasingly small, the resistance of the flow channel increases, the response of expansion and contraction of the balloon portion driven by the gas becomes poorer, and consequently a timing lag of the expansion or contraction is liable to occur and assisting action to the heart can not be achieved effectively.
The period of expansion and contraction of the balloon portion is, for example if the heart beat is 100 beats per minute, a period of 0.6 second. The gas passes back and forth inside the lumen of the outer tube within a time shorter than that period, so the smaller the resistance of the flow channel the better.
As explained above, however, the inner tube is placed inside the lumen of the outer tube and there are limits to how small the outer diameter of the inner tube can be made. Further, there are limits to how small the outer diameter of the outer tube can be made.
Therefore, in the prior art, there was no choice but to set the outer diameter of the outer tube forming the catheter tube as large as possible within a range not causing a remarkable increase in the discomfort to the patient. In order to obtain a satisfactory level of response in the expansion and contraction of the balloon portion, the discomfort to the patient was unavoidably increased to a certain extent.
The present invention was made in consideration of this actual situation and has as its object the provision of an innovative balloon catheter which enables an improvement in the response of expansion and contraction of the balloon portion despite being able to reduce the outer diameter of the outer tube forming the catheter tube and alleviating the discomfort to the patient.
To achieve the above object, the first balloon catheter according to the present invention comprises an outer tube having a first lumen inside the outer tube, a balloon portion having a proximal end of the balloon portion joined to a distal end of the outer tube and a distal end of the balloon portion joined to a tubular shaped front tip portion in order to form a balloon space inside the balloon portion, into which a pressurized fluid is introduced and released from through the first lumen of the outer tube to give an expanded and contracted state, and an inner tube having a second lumen inside the inner tube extending inside the first lumen of the outer tube to freely slide in the axial direction, projecting out from the distal end of the outer tube, and detachably attached to the front tip portion.
The second balloon catheter according to the present invention comprises an outer tube having a first lumen inside the outer tube, a balloon portion having a proximal end of the balloon portion joined to a distal end of the outer tube and a distal end of the balloon portion joined to a tubular shaped front tip portion in order to form a balloon space inside the balloon portion, into which a pressurized fluid is introduced and released from through the first lumen of the outer tube to give an expanded and contracted state, and a valve element through which a guidewire extending inside the first lumen of the outer tube to be freely slidable in the axial direction can be passed in a detachable manner, the valve element being attached to the front tip portion so as to maintain the inside of the balloon portion sealed in both the state with the guidewire attached and the state with the guidewire not attached to the valve element. Note that in the present invention, the xe2x80x9cguidewirexe2x80x9d is not particularly limited in material. The term is used in the sense including a member comprised of a rod made of a synthetic resin in addition to an ordinary metal guidewire.
In the present invention, the cross-sectional shape of the outer tube is not particularly limited. It may be circular or polylateral in shape, but a circular shape is preferable. At the inside of the outer tube is formed a lumen along the longitudinal direction.
In the present invention, the balloon portion is formed by a tubular film in which a balloon space is formed. In the expanded state, it has an outer diameter larger than the outer tube. In the expanded state, the cross-sectional shape of the balloon portion is not particularly limited and may be circular or polylateral, but it is preferably circular.
At the inside of the tubular front tip portion is preferably attached a valve element sealing the balloon space inside the balloon portion from the outside of the balloon portion. To this valve element, preferably a distal end of the inner tube (or guidewire) is detachably attached. This valve element can seal the balloon space at the inside of the balloon portion from the outside of the balloon portion both in a state with the distal end of the inner tube (or guidewire) attached to the valve element and in a state with the inner tube (or guidewire) detached. The valve element is not particularly limited. It is not limited to a duckbill valve or other hemostatic valve normally used as a medical part. A three-way cock valve, compression spring valve, water absorbing polymer slit valve, etc. may also be mentioned.
The valve element preferably used in the present invention is formed with a tight-fit hole. In the state with the distal end of the inner tube inserted into the tight-fit hole, the clearance with the inner tube (or guidewire) is sealed. In the state with the inner tube (or guidewire) detached from the tight-fit hole, the tight-fit hole closes to enable the balloon space at the inside of the balloon portion to be sealed from the outside of the balloon portion.
Preferably, the maximum outer diameter of the valve element is larger than the inside diameter of the front tip portion in the state before the valve element is attached to the inside of the front tip portion, and the valve element is compressed and elastically deformed and attached to the inside of the front tip portion in the state with the tight-fit hole closed.
Preferably, in the state with the distal end of the inner tube (or guidewire) inserted into the tight-fit hole of the valve element, the tight-fit hole stretches and an extra clearance space for elastic deformation of the valve element in the axial direction is formed inside the front tip portion.
To create this extra clearance space inside the front tip portion, preferably the inside of the front tip portion is provided with stopper members positioned at both sides of the valve element in the axial direction. The stopper members are constructed to allow passage of the inner tube (or guidewire).
The Shore A hardness of the valve element is preferably not more than 30, more preferably not more than 20, particularly not more than 15 and may be even less than 5. The Shore A hardness is measured based on JIS K6253.
The breaking elongation of the valve element is preferably 300 to 1000%, particularly preferably 500 to 800%. The breaking elongation is measured based on JIS K7311.
The compression modulus of elasticity of the valve element is preferably 0.01 to 0.30 kg/cm2, more preferably 0.05 to 0.15 kg/cm2. The compression modulus of elasticity is measured based on JIS K7208.
The front tip portion is preferably comprised of a member which can elastically deform to the outside in the radial direction.
The front tip portion preferably is provided with a pressure sensor for measuring the blood pressure etc.
The balloon catheter according to the present invention preferably further comprises a supporting rod member having a distal end joined to the front tip portion and extending inside the balloon portion and the outer tube in the axial direction separate from the inner tube (or guidewire). This supporting rod member is preferably comprised of a tube. Inside the tube is preferably passed or buried wiring from the pressure sensor.
Preferably the proximal end of the outer tube is connected to a connector and the proximal end of the inner tube (or guidewire) is detachably attached to the connector. The proximal end of the supporting rod member is preferably connected to the connector. A terminal takeout portion for the wiring passed through or buried in the tubular supporting rod member is preferably formed in the connector.
In the first balloon catheter according to the present invention, since an inner tube is attached along the axial direction inside the balloon portion and the outer tube when inserting the balloon catheter into a blood vessel or other body cavity of the patient, by passing a guidewire inside the second lumen of the inner tube, it is possible to adroitly guide the balloon portion of the balloon catheter to a predetermined position inside the body cavity.
By pulling out the inner tube from the proximal end side of the balloon catheter positioned at the outside of the body after positioning the balloon portion at the predetermined position inside the body cavity, the inner tube no longer exists inside the outer tube forming the catheter tube. Around this time, if necessary, the guidewire may also be pulled out from the proximal end side of the balloon catheter and then the balloon catheter used for treatment.
Note that in the second balloon catheter of the present invention, there is no inner tube attached from the very start. Therefore, when inserting the second balloon catheter into a blood vessel or other body cavity of a patient, by passing the guidewire along the inside of the first lumen of the outer tube and the balloon portion, it is possible to adroitly guide the balloon portion of the balloon catheter to a predetermined position inside the body cavity. Next, in accordance with need, the guidewire is pulled out from the proximal end side of the balloon catheter and the balloon catheter is used for treatment. In this state, both the first balloon catheter and the second balloon catheter according to the present invention become the same.
In this state, in the first and second balloon catheters of the present invention, the cross-sectional area of the flow channel of the first lumen of the outer tube forming the catheter tube becomes larger by the amount of the removal or nonprovision of the inner tube. As a result, the cross-section of the flow channel for feeding pressurized fluid inside the balloon portion becomes larger and the response of expansion and contraction of the balloon portion is remarkably improved. Further, this means that the same or better response characteristics of expansion and contraction of the balloon portion as in the prior art can be obtained even if making the outer diameter of the outer tube forming the catheter tube smaller than the conventional balloon catheter.
This point is also preferable since if the outer diameter of the outer tube forming the catheter tube can be made smaller, the discomfort to the patient can be alleviated.